Post [Q] Backend Platform recommendation

Dear XDA Community,
I m building with some colleagues an app. We finished the front end and are thinking about starting the backend.
The thing is we don t have any experience in backend business, servers, clouding etc. (yes, noobs but learning )
we could have a friend setting the app for us on the cloud. But he won’t have the time to manage the platform once the app is “plugged in”

My question is the following: What kind of platform (iaas, paas, saas) would you recommend for an app so that there is no much work and knowledge required once it’s plugged in in the platform?

The app is quite similar to instagram, with pictures sharing and Push notifications.

Thank you very much in advance